Ptelea trifoliata, commonly known as the common hoptree, wafer ash, or stinking ash, is a dense, rounded deciduous shrub or small understory tree native to North America. As one of the northernmost representatives of the citrus (Rutaceae) family, it is highly valued for its adaptability, low maintenance, and significant wildlife benefits—particularly as a crucial larval host plant for the giant swallowtail butterfly.

This tree grows 10-20' tall and wide, and thrives equally well across full sun, partial shade, or deep shade.  It prefers well-drained loams, but tolerates a wide spectrum of soil types, including sandy, rocky, clay and dry soils.

The flowers are small, greenish-white star-shaped and emerge in terminal clusters during late spring (May to June). They are mostly unisexual, not highly showy, and release a distinct malodorous scent that primarily attracts carrion flies, bees, and ants for pollination.

It was historically used by 19th-century German immigrants in Texas as a direct bitter substitute for true hops when brewing beer.

Host plant for the Giant Swallowtail, Thoas Swallowtail, and the endangered Schaus Swallowtail butterflies.